Fractional flow reserve(FFR) is an Intra coronary hemodynamic parameter promoted recently to assess the physiological impact of a coronary lesion . Though it sounds logically attractive the concept is sailing in rough seas .I am afraid FFR is drowning a fairly useful tool of IVUS along with it !

Read this large study on FFR (JAMA June 2014) .It seems to suggest FFR is a costly and unnecessary accessory in cath lab

Critical thoughts on FFR

It adds time , money , and procedural risk* to any given patient .The only possible use is to reduce the proliferating stent usage !But the irony is complete as we do our daily business in modern cath suits .To negate one indulgence we need to need to indulge in another ! (Junk begets Junk !)

It reflects lack of courage on the part of cardiologists to advice medical management even in obvious low risk lesions !

It is unfortunate ,we need a scientific or a pseudo scientific tool to lift up our sagging medical intellect !

* crossing delicate and often complex lesions without any major purpose is bad wisdom !(more…)

On safety issues FFR is a suspect.( Often times , it requires expertise comparable to that of a complex PCI !) .Beware , the FFR unit has stiff catheter system and is an additional health hazard . I have witnessed atleast two cases where insignificant lesions were made significant by FFR related Injury .

And now the knock out punch , ! Probably the most vital issue for which FFR should be banished * , it is not taking into accountof vulnerabilty of a plaque .( An FFR > .9 with a hanging , eccentric , mid LAD lesion was left alone by one of the academically up to date , evidence based interventional cardiologist! )

(*If perfomed in isolation without IVUS/OCT )

I am still wondering how this concept came into cardiologist domain and into the cath lab .It should have never been let out of theoretical physics labs !

Final message

The best way to assess physiological significance of an anatomical obstruction is to do exercise stress test .

If the lesion is able to sustain good exercise capacity , it can be deemed physiological unimportant.

While , this is an explicit proof in single vessel disease , even in multivessel CAD , EST is a collective measure of coronary reserve flow .( Something like instantaneous equivalent of virtual multivessel FFR )

Moderated After thought

FFR is a highly specialized theoretical tool , that has very limited role in cath lab .

The two major practical (Non academic) use of FFR is to shun away those internet fed , annoying, pseudo intellectual patients , who constantly ask for angioplasty for obliviously insignificant lesions !

FFR comes very handy to bail out cardiologists at times of distress ! (To escape from the wrath of our patients after a sub optimal & technically inferior PCIs and in the long term confabulations in restenosis after stenting ! )

How to manage an asymptomatic 45 year old man with 90 % mid LAD lesion , with FFR .9 who is stress test positive at 9 Mets ?

Six cardiologists and six responses . . . and the elusive seventh sense

FFR is most scientific test to assess physiology of coronary stenosis . I will go with that and put this patient under medical management.

I agree with FFR, still the patient has no symptoms , but why the hell is EST + ve ? I am confused .

I would definitely stent the lesion irrespective of the symptoms .

I would order a stress thallium . I do not believe in FFR

The data provided is insufficient. I would like to this patient in my clinic , and if necessary may order a fresh CAG.

For a 90 % LAD lesion FFR should not have been done in the first place .That is the root of the confusion. He should have received a stent long back .

Final message

FFR is a terrible concept for two reasons . One , it never bothers about flow across a lesion. It simply relies upon pressure drop. we all know there is an intricate relationship between pressure and flow . Simple pressure drop can never be expected to translate into incremental flow in biological systems .The second major limitation is it ignores the morphology of the lesion . We know an eccentric soft lesion with a good distal FFR is live coronary explosive .

Fractional flow reserve is a new coronary hemo-dynamic para meter used to assess physiological impact of border line lesions in coronary artery disease. The calculation is simple

FFR is a terrible concept * for two reasons .

One, it never bothers about flow * across a lesion. It simply relies upon pressure drop. We know there is an intricate relationship between pressure and flow . Simple pressure drop can never be expected to translate into incremental flow in biological systems .

FFR / OCT combo, increase not only the fluroscopy time , this procedure can be more complex than the intended PCI .

My colleagues tell me FFR measurements are not often reproducible .(I have little experience in this )

Adenosine induced vasodilatation is not natural physiological model . Further it has a potential for a coronary steal if there is near critical lesion in contra lateral artery.

There are many occasions FFR wire has caused dissection and subsequent stenting was necessary .(The very thing the cardiologist wanted to avoid !)

Bifurcation lesion FFR measurement is prone for errors

FFR in two tandem lesions cannot be assessed accurately

Post PCI FFR is not practiced routinely in may centers the fear of status quo of FFR.

Final message

This post is not to defame the FFR as a concept . Just to make you think . . . how often , we are entrapped in a pseudo -intellectual game in the cath lab ! FFR as a tool , can still be valuable to assess coronary hemo-dynamics in a selected lesion population especially, discrete, single vessel , or left main disease with around 70 % narrowing . But never go with FFR alone .Consider the morphology , location of the lesion .

Finally do not forget , the good old EST can give a stiff fight for supremacy over FFR in terms of assessing physiological impact of a coronary stenosis (Especially in single vessel disease )

Even as we make rapid strides in conquering coronary atherosclerosis by all those fancy gadgets , the fundamental coronary hemodynamic principle is poorly understood . Hence there is no surprise for the “perennial ambiguity” in the indication and effectiveness of coronary revascularization .

Why the hell , reliving a coronary obstruction may not provide the expected hemodynamic benefit or do not prevent future heart attack in many ?One of my patients asked ?

I told him . Wait , do not get excited , we also do not know . . .We are just beginning to understand mysteries of coronary circulation.

It is a well documented fact ( but a debatable ) that lesser the severiity of a lesion more likely it is prone for an acute coronary event .( Vulnerability , shearing stress or is it a simply a statistical mirage !) While the vulnerability aspect is complex , the hemodynamic impact of coronary lesions is relatively better understood. Here is an important documentation from Dr B . K Koo from Seoul , South Korea who has elegantly shown the behavior of fractional flow reserve (FFR ) in various grades of stenosis .This study was done in jailed side branches following PCI.

FFR shows a surprise relationship with severity of coronary stenosis . Even severe lesions showed equal if not more flow reserve ?

and mild lesions might have lost all its reserve.

How is it possible ? Can it be true ?

Yes , it is indeed a fact . God generally keeps a stong link between anatomy and physiology , structure and function . But he adds a rider and keeps a reserve in every human cell meant for emergency back up . FFR is one aspect of this , we have partially discovered . When we fail to understand this we are bound to get confused and make a wrong decision in cath lab.

Simply stated , flow across a coronary artery is much more depedent on the status of microvascualture than the hurdles they face in the epicardial highways !